JPS6235822A - Injection molder - Google Patents

Abstract

PURPOSE:To prevent material from stagnating and consequently enhance the accuracy in metering and in injection and prevent resin from solidifying and clogging between an injection cylinder and an injection plunger by a structure wherein the injection plunger of the injection molder consists of a plunger part and a guide part, both of which are stepped and a passage for discharging leakage resin at the stepped part of the injection cylinder. CONSTITUTION:Supplied molding material is sent by a screw 10 while being melted by heating a heater 15 and kneaded by the screw so as to be stored in a material storage chamber 3 through the retreating of an injection plunger 2. The metering of the material is completed by stopping the screw 10 by means of a limit switch for detecting the amount of the retreat of the injection plunger 2. After the material storage chamber 3 is pressurized and consequently a check valve 27 is closed, the molding material in the material storage chamber 3 is injected into a mold. An infinitesimally small portion of the resin, which flows out on a guide part 2b side through a sliding surface between an injection cylinder 1 and a plunger part 2a, is discharged through a passage for discharging leakage resin 5 and no stagnation and solidification of the resin develops between the cylinder 1 and the part 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection molding machine that is capable of accurately injecting a small volume of synthetic resin or the like. - (Problems of the prior art to be solved by the invention) Conventionally, the injection amount of a screw in-line injection molding machine is determined by the product of the cross-sectional area of the screw and the stroke. However, it is impossible to arbitrarily reduce the cross-sectional area of the screw due to conditions such as the depth of the groove or mechanical strength, so if the injection amount is small, the stroke of the screw will inevitably be short and K had the problem of requiring extremely high-precision control in order to increase the injection accuracy with the stroke.

On the other hand, in a conventional screw-library molding machine, the material in the heating cylinder is plasticized by a screw, and the material is supplied to the material storage chamber at the tip of the injection cylinder via a supply member perpendicular to or oblique to the skiffle shaft, and then the material is plasticized by the plunger. The injection amount is determined by the product of the cross-sectional area of the plunger and the stroke, so if the injection amount is small, the injection accuracy can be improved by making the plunger's cross-sectional area smaller or by making the stroke longer. However, when material is supplied to the tip of the injection cylinder, the material is supplied from the nozzle side to the plunger side by the retreat of the plunger, so the material that entered the injection cylinder first is injected later. This tends to cause material to accumulate on the injection plunger side, and there is also a corner at the connection between the supply pipe and the injection cylinder where it is difficult for the material to flow, which tends to cause material to accumulate. For this reason, if the material remains for a long time, it may cause burning of the material, and there are also problems such as difficulty in changing the color (material).

(Object of the Invention) The present invention was devised to solve the above-mentioned problems of the conventional art.
The injection plunger inserted into the material storage chamber is composed of a plunger part and a guide part at different levels, and a resin discharge passage is provided in the different level part of the injection cylinder.This is a combination of a plunger type injection method and a two-screw plasticizing method. In addition to preventing material from stagnation, the diameter of the injection plunger and roller is reduced to lengthen the stroke required to inject a small volume of material, improving metering accuracy and injection accuracy, and preventing leakage from between the injection cylinder and injection plunger. The purpose is to ensure that the resin is discharged and to prevent the resin from solidifying and clogging between the injection cylinder and the plunger.

(Structure of the Invention) The injection molding machine of the present invention has an injection cylinder equipped with a nozzle and formed with a material storage chamber, and a heating cylinder in which a screw is inserted between the material storage chamber and the material storage chamber. The invention is characterized in that the injection plunger of the injection molding machine is provided so as to be movable back and forth in the axial direction, and the injection plunger of the injection molding machine is connected to the tip of the heating cylinder and is fitted into the material storage chamber of the injection cylinder.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. In the figure, reference numeral 1 denotes an injection cylinder, in which an injection plunger 2 constituted by a plunger part 2a and a guide part 2b of different heights is slidably fitted. When the plunger 2 retreats, a material storage chamber 3 having an inner diameter approximately equal to that of the plunger portion 2a is formed, and a nozzle 4 is provided at the tip of the injection cylinder 1.
is attached, and a passage 5 for discharging leaked resin is bored in the middle part near the stepped part. This injection cylinder 1 is supported by left and right boats 7 provided on a frame 6 via tie bars 8.

Reference numeral 9 denotes a plasticizing cylinder, which has a hole 11 having an inner diameter approximately equal to that of a screw 10, which will be described later. A cylindrical valve component 4 having a material passage 13 continuous with the material passage 12 is installed in the hole 11 and intermittently.

Reference numeral 15 denotes a cylinder heating heater attached to the outer periphery of the injection cylinder 1 and the plasticizing cylinder 9. Reference numeral 16 denotes a water-cooled cylinder for cooling the plasticizing cylinder, and a cylindrical housing 17 is attached to the water-cooled cylinder 16. A hollow shaft 20 is attached to the housing 17 via a bearing 21 so as to be rotatable by a hydraulic motor 19 attached to one end of the housing 17 via a bearing holder 18. The base end of screw 0 is attached.

Thus, the screw 0 is connected to the bearing 2 via the hollow shaft 20.
1 is rotatably supported by a housing 17, and is configured to be rotatable within the plasticizing cylinder 9 by driving a hydraulic motor 19.

A cylinder tube of a double rod type hydraulic cylinder 22 for injection along the screw axis direction is attached to the left and right sides of the housing 17, and the tip of the piston rod of the hydraulic cylinder 22 is connected to the support 7 and this cylinder tube. Similarly, the left and right sabots (2:lC) provided on the frame 6 are installed.

Thus, the plasticizing cylinder 9 is connected to the injection plunger 2
while supporting it through the hydraulic cylinder 22? Beau)7.
23, the hydraulic cylinder 2 is operated by a switching valve 24.
2, the injection cylinder 1 can be moved back and forth in the direction of the screw axis.

A check valve 27 for preventing backflow is disposed in the material passage 13 of the valve component 14, which is composed of a ball 25 that can be seated and closed on the screw lO side and a protrusion 26 for preventing falling off and for material distribution on the side opposite to the screw 10. It is set up. Thus,
The material storage chamber 3 and the groove 28 around the screw 10 are connected by a material passage 12.13 via a check valve 27, and when the material pressure on the screw 10 side is high, the check valve 27 opens and communicates, and vice versa. When the material pressure on the side opposite to the screw 10 is high (during injection), the check valve 27 is closed and shut off.

In addition, 29 is a hopper, which is communicated with a material supply port (not shown) provided in the plasticizing cylinder 9 and the water-cooling cylinder 16.

(Function) When the screw 10 is driven by the hydraulic motor 19, the molding material supplied from the hopper 29 is heated and melted by the heater 15 and kneaded by the screw 10, and then flows into the groove 28.
The inside of the material is sent to the tip side of the screw, the check valve 27 is opened, and the material is sent into the material storage chamber 3. The injection plunger 2 is moved back to the right in the figure by the material pressure by the amount of material fed in this way, and the material is stored in the material storage chamber 3.

When a predetermined amount of material is stored, the control switching valve of the hydraulic motor 19 is closed by an IJ switch (not shown) that detects the amount of retraction of the injection plunger 2, and the screw 1
0 stops rotating and measurement is completed.

Next, when the switching valve 24 is operated from the neutral position to the right position in the drawing by an electric signal to start injection, the cylinder tube of the hydraulic cylinder 22 moves to the left in the drawing, causing the injection plunger 2 to advance. Therefore, when the material storage chamber 3 is pressurized, the check valve 27 is closed, and the injection plunger 2 moves further forward, the molding material in the material storage chamber 3 is injected into a mold (not shown).

A very small portion of the resin injected at this time flows out from the sliding surface between the injection cylinder 1 and the plunger portion 2a of the injection plunger 2 toward the guide portion 2b, but this does not occur laterally.

When the injection is completed, the mold side is cooled and released, and at the same time, the screw lO starts metering work (plasticization, kneading, V-extrusion), and supplies the molding material to the material storage chamber 3 in the above-mentioned process. Effects of the Invention) As described above, this invention uses an injection plunger that is concentric with the screw and independent, so the diameter of the plunger can be made arbitrarily small regardless of the screw diameter. Even with the injection amount, it is possible to take a certain amount of injection stroke, improving metering accuracy and injection accuracy, and because plasticization and kneading can be performed with a large diameter screw as in conventional methods, the plasticization rate is high, Forming efficiency is also higher than in the case of small diameter screws. Also, unlike screw pre-plastic molding machines, it uses a first-in, first-out system.
In addition, since there are no corners in the material passageway where the material does not easily flow, there is no accumulation of material that may cause burns. Further, since the leaked resin from the sliding surfaces of the injection cylinder and the injection plunger can be reliably discharged, the leaked resin does not solidify and impede the sliding movement of the injection plunger.

Therefore, it is possible to easily adapt to the size of the product, maintain the quality of the product very well, and improve molding efficiency.

[Brief explanation of the drawing]

1 and 2 are plan sectional views showing an embodiment of the present invention,
It is a front view. 1... Injection cylinder 2... Injection plunger 2a... Plunger part 2b... Guide part 8.
... Tie bar 9 ... Plasticizing cylinder 10
...Screw (groove 23) 12, 13...Material passage 15...Cylinder heating heater 16...Water cooling cylinder 17...Housing 19...Hydraulic motor 20...Hollow shaft 21...・Bearing 2
2...Hydraulic cylinder 24...Switching valve 27...
・Check valve

Claims (1)

[Claims] A heating cylinder, in which a screw is fitted concentrically with the material storage chamber, is provided to the injection cylinder to which a nozzle is attached and a material storage chamber is formed so as to be movable back and forth in the direction of the screw axis. The injection plunger of the injection molding machine has an injection plunger inserted into the material storage chamber of the injection cylinder connected to the tip part, and is composed of a plunger part and a guide part of different steps, and a part for discharging leaked resin is provided at the different steps of the injection cylinder. An injection molding machine characterized by having a passage.